Inkjet recording method is a printing method of forming characters and images on recording media by ejecting ink droplets from very fine nozzles directly to the recording media, and attaching the ink thereto. The apparatus used in the above-described recording system has advantages that it makes low noise, and is easy to handle. In addition, there are other advantages that colorization of this recording system is easy, and plain paper can be used as the recording medium (hereinafter referred to as printing medium). Therefore, apparatuses on this recording system are widely used as output machines in offices and homes.
Meanwhile, for the industrial use, with the improvement of inkjet technology, the use as a digital printing output apparatus is expected. Actually, printing machines using solvent inks and UV inks which can print on plain paper and unabsorbent media (for example, plastic base materials such as PVC and PET) are commercially available. However, in recent years, from the viewpoint of ecological friendliness, demands for aqueous inks are increasing.
For aqueous inks for inkjet, as seen in Patent Literatures 1, 2, and 3, inks used for printing on paper media including plain paper and exclusive paper such as photographic glossy paper have been developed for a log time. Meanwhile, in recent years, applications of printing of the inkjet recording system are expected to expand, and there is an increasing demand for direct printing on low water absorbing printing media such as coated paper and unabsorbent base materials used for, for example, outdoor advertisement. Conventional aqueous inks are assumed to be used for drawing carried out by making the ink droplets absorbed in a paper medium, therefore the suitable printing media are limited. When a conventional aqueous ink is used for printing on a printing medium with low water absorbency, image bleeding occurs, therefore improvement is desired.
In response to this, Patent Literature 4 discloses that direct printing can be carried out without causing bleeding on coated paper by using an ink composition containing a crystalline glycitol. This ink composition decreases ink flowability and prevents image bleeding through the crystallization of the crystalline glycitol after printing. However, when this ink composition is used, if the crystalline glycitol remains in the coating film, the crystalline glycitol dissolves when, for example, fouling is wiped from the printed material with an alcohol solvent or detergent, which can cause problems such as deterioration of the coating film.